Electric impulse generator



June 2, 1942. R. HELMERT 2,285,088

ELECTRiC IMPULSE ENERATOR Filed July 29, 1939' hunter: J fiafierm'lmew' Patented June 2, 1942 ELECTRIC IMPULSE GENERATOR Robert Helmert, Berlin, Germany, assignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof, Germany, a company Application July 29, 1939, Serial No. 287,197

. In Germany July 30, 1938 4 Claims.

,As is well known, when transmitting switchin impulses of audio frequency along telephone lines the audio energy thus transmitted may happen to be of a form not unlike the switching impulses, thus giving rise to a possibility of wrong connections. In order to avoid this possibility it has been proposed to transmit the switching impulses by means of two alternating currents which are of difierent frequencies and are emitted alternately at a third frequency rate.

The invention is concerned with a transmitting arrangement which is adapted to produce in an extremely simple manner the mixture of switching frequencies necessary for the aforesaid purpose. In a preferred form, transmitting arrangement comprises only a tone generator and a polarized relay. The arrangement is such that the contact of the polarized relay shall, without the aid of auxiliary relays, act to change the frequency of the tone generator and also to control the relay itself. The time constant of the relay circuit is selected in a well known manner so that the relay will operate at a desired third frequency.

The accompanying drawing is a diagrammatic representation of one embodiment of the invention.

In the circuit shown a tone generator comprises an amplifier l having a tuned input and output mutually related by transformer means SU. The tuned circuit, which is so related to the input and output circuits of the amplifier, in

the form shown includes the inductance III/IV of the coupling to the amplifier and capacitance means. Further coupling means associated with the transformer SU provides an appropriate output connection for the circuit. 7

In accordance with features of the invention the tone generator is adapted alternately to supply a plurality of different frequencies, successively keyed in accordance with a tuned relation. In the form shown this successive supply of different frequencies is accomplished by providing means for successively changing the circuit constants of the tuned circuit. To this end, a relay TR. having contacts tr is made in one contact position 8 to provide an oscillating circuit including capacitances C2 and C3, each shunting the winding III/IV, and in another contact position I the constants of the tuned circuits are changed by addition of capacitance C4 and a certain amount of resistance. Thus, in position 8 of the contacts tr, a signal of one frequency is produced, and in position 1 a signal of another frequency may result, as will be clear.

In accordance with further features of the invention, I provide means for operating the relay TR so that the tone generator will produce switching impulses of a plurality of frequencies for transmission alternately and at a predetermined rate. In the form shown, relay TR has two windings V and VI connected on one side to a common point I, 2. The relay windings are connected in parallel and each is supplied with biassing energy from an adjustable point on a potentiometer Rs, bridging a source of direct po.- tential; however, the circuit of winding V is provided with a capacitance C5 for purposes that will later become apparent. A resistance R5 is connected between one side of the potentiometer R6 and the winding common point I, 2, and contact I of relay TB. is electrically associated with the relay winding side of resistance R5. The other side of the potentiometer R6 is directly connected to the winding III/IV, which forms the inductance of the tuned circuit.

With the above-described circuit it will be seen that relay TR may be made to alternate in its position in accordance with the charge and discharge times of condenser C5, winding VI being effective as the operating winding and V as a delay winding.

Thus, with contact tr in the position shown a negative potential is applied over R5 to the junction points I, 2 of relay TR. As a result, a current fiows over winding VI, the operating winding of TR. in such direction that contact tr is switched. As soon as tr arrives in the position 1 the direction of the current in winding VI of relay TR is reversed and. condenser C5 begins to discharge. This reversal in potential occurs as a result of contact 1 short circuiting R5 and the voltage 24V. The potential then effective upon windings V and VI is derived from the other portion of potentiometer Re. Thus, an opposing potential is applied to the relay winding and this potential must work against the charge on C5 in order to operate winding VI in the other direction to return tr to position 8. The discharge current for condenser C5, that is, the current flowing through winding V of TR may be slow to decrease due to the circuit time constant. Thus, at first it may prevent the reversal of the magnetic field of TR and hold contacts tr in position 1. After decrement of this discharge current the contact tr is restored into its position at 8, since now the current is acting in TR. VI only. On opening contact trl, the short circuit is removed, and the direction of the current in TR is again reversed. The charging current for C5, now flowing in the reverse direction, at first, and for a controllable time interval, again acts to prevent the reversal of the field, and so on. By adjusting a potentiometer R6 the two branch voltages which act upon relay TR with contact trl either opened or closed are predetermined and may be adjustably controlled. In accordance with the invention these branch voltages may be so adjusted that the operating time of relay TR shall be longer in one position than it is in the other, i. e., so that contact tr8 shall be open as long as it is closed, and vice versa. As a result each of the two frequencies to be emitted by the tone generator may be produced as long as the other.

It will at once be apparent that the output of the tone generator may be employedlwithifurther circuits as a source of switching impulses'of two frequencies alternately emitted at a predetermined rate.

While. the invention has been described in particular detail in connection with the preferred form shown, it is of course to be understood that many modifications, additions, and omissions may be made within the scope of the invention, as defined by the followingclaims.

Since itis wellrknovvn that any circuit branch including a series condenser responds only to potential variations and is unaffected by constant D.. C. potentials superposed on such variations, it is reasonable in defining aconnection of such a branch between two specified circuitpoints (such as V and the center tap of R6) to include in the definition not only the connection of such branch directly between the specified points but also the equivalent connections derived by shifting one end of the branch from the corresponding one of the specified points (e. g. from the center of Re) to a closely relatedpoint (e. g. one end of Re) which differs only by a substantially constant D. C. potential but has essentially the same potential variations and also to include the connections derived by similarlyshifting both ends of the branch. Accordingly a statement. that a branch is connected in respect to potential variations efiectively between two specified points shall hereinafter mean that the branch is connected between two points whose potential variations are essentially the same as those of the specified points.

What is claimed is:

1. A signal generating arrangementifor alternately emitting two signal frequencies ata predetermined rate comprising a tone generator, a tuned circuit associated therewith having a plurality of component elements, and means for changing the effective value of said circuit comprisinga relay having two windings. an tarmature and a pair of contacts, one end of each of said windings being connected at a. common point and the other ends of said windings being separate, a resistance connected to said common point, a source of voltage, a voltage divider having first and second end terminals and an intermediate. tap connected across said source to divide the voltage of said source into a first component voltage between said first end terminal and said intermediate tap, and a second component voltage between said intermediate tap and said second end terminal, means for connecting said intermediate tap to the separate end of one of said windings and for connecting said first end terminal to said resistance whereby said first component voltage is applied in series with said resistance across said one of said windings, means for connecting said second end terminal to said armature, means for connecting one of said contacts to said common point, means for connecting the other of said contacts to an intermediate point of said tuned circuit, and a time delay circuit connected between the separate end of the other of said windings and said voltage divider.

2. An arrangement according to claim 1 wherein said time delay circuit comprises a condenser connected between the separate end of the other of saidwindings andsaid intermediate tap of saidpotentiometer.

3. A- signal generating arrangement for alternately emitting two signal frequencies at. a predetermined rate, which comprises a polar relay having an operating winding and a delay winding. and onlyone changeover contact setincluding first andsecond fixed contacts and a-movable conductor adapted to close. againstcsaid first or said second contact. responsive to energization of said operating winding in a givensense or the opposite sense respectively; firstcurrent supply means; a resistor; first operating connections connecting said first supply means in series with said operating winding. and said resistor with such polarity as tolenergize saidwinding in said given sense in the absence of other connections; further currentsupply means; further operating connections connecting said further supply meansin series with said operating winding, said conductor and said. first contact with suchpolarity as to energize said winding in said opposite sense responsive to closure of said conductor against said first contact; a condenser connected in series with said delay winding to form a-circuit branch responsive only to potential variations; means connecting said circuit branch effectivelyacross said operating winding in respect to potential variations, said delaywinding being poledtoinitially opposesaid operating winding in response to any abrupt potential variation; a tone generator having a tuned circuit-for controlling its frequency; and connections from said second contact and said movable conductor to twoflpoints of said tuned circuit for varying the frequency of said tuned circuit responsive to closure of said movable conductor against said second contact,

4. An arrangement according to claim 3 wherein said first current supply andsaid further current supply are constituted by a common current source and anadjustable voltage dividing potentiometer connected across said source and tapped to form said first and second current supplies ROBERT HELMER'I. 

